Field of the Invention
The present invention relates to a driving technique of an electro-optical device configured by using an electrochromic material.
Description of the Background Art
In the international publication WO2012-118188 pamphlet, there is disclosed a light-adjusting element comprising a pair of substrates; a pair of electrodes formed on surfaces of the pair of substrates that face each other, one of the electrodes being a transparent electrode having nano-order depressions and protrusions; and an electrolyte layer that is interposed between the pair of electrodes and includes electrolytes, a mediator, and an electrochromic material that contains silver. When voltage is applied between the pair of electrodes of this light-adjusting element, in one electrode of this light-adjusting element, silver ions in the electrochromic material are reduced and deposited as silver to form a film, and then the deposited silver is dissolved as silver ions when the voltage is released. In this case, if the silver is formed on a smooth electrode, the outer appearance is in a mirror surface state. And if the silver is formed on a particle-modified electrode, the outer appearance is in a dark state (black state) due to irregular reflection of light. Thus, by making one of the pair of electrodes smooth and the other particle-modified, it is possible to switch between the mirror surface state and the dark state according to the polarity of the voltage. Further, when the voltage is released, the area between the substrates becomes transparent (a light-transmitting state).
While the light-adjusting element described above allows switching between the mirror surface state and the dark state according to the polarity of the voltage and thus is unproblematic if used as a singular element, malfunction and damage may occur between adjacent elements when a plurality of these light-adjusting elements is aligned side by side constitute a display device or the like.
For example, assume that voltage (+2.5 V, for example) is applied to one light-adjusting element (here referred to as a “first light-adjusting element” as a matter of convenience) so that the potential of the electrode on one substrate side becomes relatively high to achieve a dark state in outer appearance, and voltage (−2.5 V, for example) is applied to another adjacent light-adjusting element (here referred to as a “second light-adjusting element” as a matter of convenience) so that the potential of the electrode on the other substrate side becomes relatively high to achieve a mirror surface state in outer appearance. In this case, a high voltage (5 V, for example) equivalent to twice the amount of voltage applied to each of the elements is applied between the electrode of the first light-adjusting element and the electrode of the second light-adjusting element on one substrate side. When such a transverse-direction voltage (a horizontal voltage with respect to the substrate surface) occurs, an oxidation-reduction reaction (electro-deposition) occurs in the electrolyte layer that exists between the electrodes, causing malfunction. Specifically, a deposited film of silver or the like occurs between the electrodes and, without sufficient voltage being applied to the first light-adjusting element and the second light-adjusting element, respectively, the reaction in the electrolyte layer is inadequate and the intended operation (a dark state or a mirror surface state) is no longer achieved. Further, an organic solvent of the electrolyte layer has a potential window, and applying a high voltage that exceeds that range is not preferable in terms of element durability. While the time period during which high voltage is applied is preferably short, continually applying voltage for a long period of time (1 second or longer, for example) may damage the organic solvent, resulting in air bubbles and damage to the element.
It is therefore an object of specific aspects according to the present invention to provide a technique that makes it possible to prevent damage and malfunction in an electro-optical device in which a plurality of electro-optical elements (light-adjusting elements) that use an electrochromic material is configured side by side.